Climbing the walls – gecko-style

24 September 2009

Two scientists have discovered that the ability of the gecko to grip onto smooth surfaces is actually triggered by gravity, and that it is the steepness of a surface that makes them deploy their gripping mechanism. These findings and future results may have applications in the medical world, space travel, and in robotics, to name but a few.

The researchers, from the University of Calgary and Clemson University, have been examining how and when geckos use their specialized toepads to attach to surfaces under different circumstances.

Published in the online edition of the Proceedings of the Royal Society [DOI: 10.1098/rspb.2009.0946], the research showed that the adhesive system was turned on when a surface was inclined to at least 10 degrees, regardless of the type of surface involved.

It was known how geckos are able to stick to most surfaces but not what actually triggered the use of the adhesion system. The setae, the bristles that cover their toes, and the microscopic, hair-like filaments called spatulae that are attached to them, give the geckos the ability to grip, but it is also crucial that they are able to turn the adhesion system on and off easily as they move across a surface.

An interest in evolutionary biology and how animals respond to particular challenges led the researchers to explore how natural selection has created an system that enables geckos to deploy their special grip when needed.

A key insight of their research was in showing the importance of feedback and perception for the gecko, when it was realised that geckos never use their clinging mechanism when on the horizontal, even when that surface is extremely slippery. Russell explains that “it may be disadvantageous for geckos to use their adhesive system on level surfaces. We know that it would slow them down, but we don’t know if there are other physical limitations that would render such a system less effective if not assisted by gravitational loading that can be experienced in body orientations beyond the horizontal.”

The hope is that an understanding of the geckos’ in-built traction system will have commercial potential, from a use in space exploration, to military applications such as in bomb disposal, to medical uses such as bandages, or even in the area of robotics. As Higham points out, “a robot could potentially be faster when moving on a level surface by not adhering. When the robot encounters an incline, it could then deploy the system and climb.”

Russell and Higham now aim to continue by observing different types, sizes and ages of gecko, to see how the adhesive system is deployed in other species of geckos, which will help them better understand the extensive diversity of such systems.

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